The present invention relates to an image forming apparatus, an image forming method and a computer-readable storage medium having an image forming program. More particularly, the present invention relates to a portable and simple image measuring technology utililized for surveying and making a drawing in a land surveying field, which uses digital processing by digital photogrammetry and a personal computer.
Specifically, the present invention relates to an image forming technology for forming a digital orthogonally projected image (ortho-image) from one to a plurality of images to be superposed on the drawing when a drawing of a site to be measured is made. The present invention relates to an image forming technology which enables any operator to easily make a drawing of an orthogonally projected image by using a survey instrument and images so as to stick an ortho-image to the drawing, and also enables a digital orthogonally projected image to be generated and rectified such that the situation of a site to be measured can be understood in detail. An object of the present invention is to provide an image which enables stable stereo analysis to be performed even for a stereo-image.
The present invention can also be applied to, for example, an image obtained by photographing a wide range divided into small images having overlapping areas with one another.
According to a prior art, a drawing obtained by surveying in a site to be measured has been made by using paper and a pencil or the like which are typically used in plane table surveying. In recent years, a line drawing of a site to be measured has been made by using a survey instrument and a portable computer in combination which are typically used in pen-based mapping system.
FIG. 18 is a view illustrating conventional stereo-image measuring. Usually, as shown in the drawing, the three-dimensional coordinates are obtained by photographing two or more overlapped images based on the principle of triangulation by stereo-image photographing. If a target range is wide, a plurality of images are photographed. For example, in even a simple site, photographing of ten to twenty images is usually necessary. In this case, unless orientation (i.e., calculating a camera position, inclination or the like) can be performed for each stereo pair (model), a stereo-image cannot be rectified. Three-dimensional measuring cannot be performed, either.